Observational evidence of quasi-27-day oscillation propagating from the lower atmosphere to the mesosphere over 20° N

Abstract

Abstract. By using meteor radar, radiosonde and satellite observations over 20 • N and NCEP/NCAR reanalysis data during 81 days from 22 December 2004 to 12 March 2005, a quasi-27-day oscillation propagating from the troposphere to the mesosphere is reported. A pronounced 27-day periodicity is observed in the raw zonal wind from meteor radar. Spectral analysis shows that the oscillation also occurs in the meridional wind and temperature and propagates westward with wavenumber s = 1; thus the oscillation is of Rossby wave type. The oscillation attains a large amplitude of about 12 m s −1 in the eastward wind shear region of the troposphere. When the wind shear reverses, its amplitude rapidly decays, and the background wind gradually evolves to be westward. However, the oscillation can penetrate through the weak westward wind field due to its relatively large phase speed. After this, the oscillation restrengthens with its upward propagation and reaches about 20 m s −1 in the mesosphere. Reanalysis data show that the oscillation can propagate to the mid and high latitudes from the low latitudes and has large amplitudes over there. There is another interesting phenomenon that a quasi-46-day oscillation appears simultaneously in the troposphere, but it cannot penetrate through the westward wind field because of its smaller phase speed. In the observational interval, a quasi-27-day periodicity in outgoing long-wave radiation (OLR) and specific humidity is found in a latitudinal zone of 5-20 • N. Thus the quasi-27-day oscillation may be an atmospheric response to forcing due to the convective activity with a period of about 27 days in the tropical region.

Quasi 10‐ and 16‐Day Wave Activities Observed Through Meteor Radar and MST Radar During Stratospheric Final Warming in 2015 Spring

“…It is interesting that the temporal variations of the zonal winds display a similarity between the WH and BJ stations; thus, the phases of the Q10DW (Q16DW) are also nearly consistent with each other at the two stations. The Q16DW has a steeper phase slope than the Q10DW; thus, the Q16DW has a longer vertical wavelength, which agrees with the previous studies (Huang, Liu, Zhang, et al, , Huang et al, ). The vertical wavelength of the Q10DW seems to be larger at the MH station compared with at the WH and BJ stations, which is likely to be in connection with the background atmospheric conditions.…”

Signature of a Quasi 30‐Day Oscillation at Midlatitude Based on Wind Observations From MST Radar and Meteor Radar

“…Figures a and b show the fitted amplitude and phase. Here, the phase is defined as the time when the wind oscillation attains its maximum (Huang et al, ; Huang et al, ). In the troposphere, the fitted amplitude has a peak value at about 9 km.…”

“…One is that GWs and tides modulated by ISOs in the lower atmosphere drive in turn the similar periodicities in the MLT by transporting their energy and momentum to the MLT (Eckermann et al, 1997;Eckermann & Vincent, 1994). The other is that ISOs propagate to the MLT from the lower atmosphere (Huang et al, 2015;Ziemke & Stanford, 1991). Some observations over the equator supported wave-induced ISOs in the MLT (Lieberman, 1998;Isoda et al, 2004;Tsuchiya et al, 2016).…”

“…In contrast to extensive studies of ISOs in the tropical region, ISOs in mid and high latitudes are paid little attention to. Radiosonde observations confirmed that ISOs not only occur at midlatitude and high latitude but also may have much larger amplitude over there than that at low latitudes (Huang et al, ). Using meteor radar data at the UK (52°N, 2°W) and ESRANGE (68°N, 21°E) stations, Pancheva et al () noticed an obvious 75‐day oscillation in the MLT; however, atmospheric wave activity, including GWs, tides and quasi 2‐day waves (QTDWs), did not exhibit a corresponding periodicity, thus exact cause of this ISO seems to remain unclear.…”

“…Correlation between diurnal tides and ISOs in the MLT was supported by subsequent works (Isoda et al, ; Kumar et al, ; Lieberman, ), and evidence of interaction between GWs and ISOs was also noticed (Tsuchiya et al, 2015; Moss et al, ). The study by Huang et al () indicated that an ISO with relatively short period of 27 days could overcome tropopause block and weak westward background wind to propagate upward into the MLT due to its large phase speed, while an ISO with long period of about 46 days does not so. By using a general circulation model, Miyoshi and Fujiwara () examined ISO excitation in the equatorial MLT, showing that interactions of mean flow with ultrafast Kelvin waves and diurnal tides play an important role in driving ISOs.…”